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March 19, 1929. c, p, MADSEN 1,705,733

SYSTEM OF SOUND GENERATORS Filed Dec. 7, 1927 2 Sheets-Sheet 1' March 19, 1929; c. P. MADSEN 1,705,733

SYSTEM OF SOUND GENERATORS Filed Dec. 7, 1927 2 Sheets-Sheet 2 mmvron (M120 1? Madaen Patented Mar. 19, 1929.

UN STA 5 1,705,733 PATENTQQFFICE;

CHARLES P. IVJQADS EN,10F cRo'roN-oN-H'UDsoN; NEW ORK SYSTEM or SOUND'GENERATORS' Application filed December 7, 1927. Serial K092324318. i

This invention relates to a system of sound generation priinarilyvadapted to the reproduction of sounds of audible frequency of M rich phonographs and 'radio loud speakers are types. a It mayalso be used inthe direct production of .sound as in stringed musical i nsti-uinents, electrically operated organs and H10 M131 '1:

Iii-apparatus now employed, themotion is alternating or oscillating; that is, it movesin its travelthrough a zero 'point; whether. the application be to a diaphragm, a cone or other body." This motion i'iniparts. the sound-pro ducing vibrations but with a reducedetfect for the reason that thepresent systefnsgare neutral and agreat part of the energy is taken up:in lost inotion-and in initiatin the vibratory actionzduetovthe inhererite asticityor comprcssibilitypof theimaterial. By a neutral system-is meantone not initially under compression or tensionorone having a slight stress at a :POlIitkOI pointsremote from the point of.actuation-.:- j: .I i- (1 invention involves the principle of placing the entire system under, a consider.- able stress and carrying thatustressto Ones near the point of actuationas' possible'j stressing of bodies -.is Avell ki 'iowmto makers of musical instruments-zand all :suchbodies are under-initial stress-,so that ,in applying my invention to i'eproduce'rs,;-I secure. great brilliance" and detail; offireproductioni com;- bined with large volume-Z An advantage accrues .in .thestressed system of my invention in that Where the sound generator is'placed-under initial stress, such as might be eompressionand parts other than the generatorar'eunder tensionfthe actuating motion is applied-in the direction oft-he strain and all lost motion anda large degree of the compressibility or give ofitheentire systemis taken up so that the soundsgenerated arise from the variation of stress produced by the actuating motion and-are instantly available without lag or distortion. I

In one of the preferred forms of my invention, I use a double cone-of pleated,-resilient material possessing a large degree of stiffness and so arranged that the cones may be drawn together and a compressionof considerable magnitude set up in theirvanes or'elements. The force necessary to do this is applied from a point as near; as possible to .thepoint of actuation and is there-balanced; In this manner the entire system is under stress and, practically all compressibility. andiall lost motion 7 having been taken -up,zis--=in an energy condition 1. e. is prepared instantaneously .to act.

Other and further-advantages will appear .in tliefollowing specification and drawings.

Inthedrawings; I

of a .sound gen "ratorembodying my invention-as applied to a phonograph L F- 2 i i v ti niins t of. a iiiii lar sound generator.

netic operation,

EIOCtIOlllflgIlQtlO operation 1,

.. *In,F1g.'-l, theso und generator is gshow-nzas preferably circular-j, and pleated, the --upper edge otthe pleatsbei-ng. indicated at 3 and 4 I}: Fig.1 is a;diagrarnmat ic sectibrial elevation arranged, for; electromagand the loyver edges-rah?)zandifi. ,i-The matei rial yt e a y; s ch as m yi-ib a apeb e o being pleated and irr should possess ,the qualit esof rigidityand resiliency. For

this purpose, I have; found Japanese; vellum tqr a e mpre nat d ifihibak t although many othensubstances may be used that have similar,characteristics; Cones 1 and 2- have .a common-meeting edge such as at ;7.vand .t i i is is preferably bound or gretained by any; suitable 1neans :one of,.wliicl would be ,a treated fabric with son 1 e ,-abilityto stretch, asindicated at 8, iTheapices; of the cones have-openingsformed b theiinner ends of theplates, the opening 0 ,the outer cone having a cone shaped. member, 9,,. Wltl1 a threaded member, 10, and a knurled nut, 11 The .opening in ape x -p;f the,inner ,con e fits, over the conical member, 12, fixed to the weight or inertia 1nass,..l3.w'It,will beseen thatthese conicalunembers-Q and .12 practically seal the .cones rand makie them almost air tight; this; giving a newgiresult over'generators of the old art nin w hich there is, an opening. The weight, 13, carries a fulcrum,

14, upon which isgseated thelever, 15, which 19, acting between it and the lever,'so thatby means of this screwthe pressure of the spring, 19, on the lever, 15, may be varied. Also threaded in a., recess of weight, 13, is stop screw 20, havin the usual lockin nut and i b C so located as to retain the lever 15 in position when the stress of the system is released. Attached to the lever, 15, and directly in line with the fulcrum 1 1 is a needle holder, 21, carrying needle;22,and-this needle isjretained in the holder by the"screw',='23.'

By turningthe'knurled-nut, 11, I' can in- 16 Sand thus'on -the lever, 15'. To balance this and keep the needle, fl2,' andi t s holiier in "approximately vevtieal' 'pcsitipn the eap screw, 18, is'tur'ned down until the pressure of spring 19, onthat-fend of lever lfi will balance "the tension of the rod,16,'on the other-end of the lever?" By" proper design of;- the spring, 19, the tension transmitted through'tlie lever, -"15,may-be-ma'de very high, even'up'to the "poin't of failure of whatever material 'may compose the cones -1' and '21 In-placing'a'tension on the wire, '17; the vanes or pleats of the cones 1 and -2,f a lre pu t in a'state'of compression an'd'this compression, as j ust stated, may

' bei'very'widely 'varied bult' in general it co'r respondsito'a tensio'n 'of several poundson the wire; 17, as lowas four and as high as pouiids';--'-depending upon-circumstances".

I when this eem ressien "is? a'ppliegii to t e conesand the system balancedas ust de- -sc'ribed itfwill be seen that'whilethe system is balaneedfitis in-a' state of strain ncit'oniy in the cones butin the associated elements as well and that this balance" of stresses is arried, close to the poiiit ofactuationfwhich "is at the needle will then be re'produced as audifblesounds-by the reproducer or sound generator s'hownf Where the tension on the wire 17; 'is of [considerable magnitude and the eonesfl' and 2 are'in compression and the lvefili'is in balance, the lost inotion of the system is practically eliminated and a large degree ofthe inherent compressibility of the cone material is taken up and the system is in what 'may' be termed an energy condition so that'the slightest movement of needle 22 is instantaneously reproduced without lag and very little energ y is iabsorbed or dissipated;

" "Another advantage resulting' from stressingthe system is that the effects of temperature-and moisture, which ordinarilycreate loose areas or otherwise affect the characteristi'cs of the'sound generator, become negligible-fo'r the reason'that whatever changes would ordinarily be brought about by temperatureand moisture variations are insignificant in comparison with the magnitude of the compressive stress under which the cones operate, and this is a benefit not found in othen-devicesof like nature. The cones l and 2, being ordinarily of pleated construction a'sdieretofore described, may have the individual vanes passing through a 90 twist drool-each apexto :its perimeter, though I preferito have slightly. less torsion than this :in'fthevanes while the device is in an inoperatiive=conditionasthis permits tuning to the desired 'pitch.' -"Phus' whilethe vanes at the apex are perpendicular with the edges 1 and -2,they=lie' in practically horizontal planes at their peri meters: This imparts a degree of torsionin each wane and While not new in the artcertaiwadvanta'ges are secured therefrom when'use'din connection with the compressive stresses."*"

"" YVhile I have-described a sound generator as being'composed-of two associated cones,

the elements of which are under considerable degree ofjstress; '1? have found that the character-of this 'stress is dependent upon the angle wli'ich' eacli" cone makes its base line, which would naturallybe the line of juncture of the cone perimeters as indicated at.24. When this angle is 30 orgreater the stress imparted to the cone vanes will be substanti'all y 'all compression as governed by the ten- *sjion plaieed flpoii Wll(, 17. 1 However, the base; angle of the cone'is less than and-especially at about 15 there will be coin'bine'dtension -and compression; the tension develo'ping near the perimeter of the cone and ez tiending practically one half of the slant height, the remainder being iinde'r compression and where this change from tension'to compression occurs there will be a neutral point. As the base angle of the cone deereas'esi'tliis neutral point will progress up the 'slantheight until the base angle is in the neighborhood of 10 at whichpoint the cone vanes willbe almost entirely=undertension. "Lhave'found'that cones'having a base angle of-30 or slight'ly over,- give superior results "so" -'tlia t it "appears that the compressive stresses are the more important and more s atisfactory'for the reproduction of sound. However, this relation of compression to tension areas maybemodified in the case of double pleated cones having-fabric bound perimeterswhen the fabric has a length somewha less "than "the perimeters of the cones so'that the angle of the cones is slightly raised. "The ratio ofcompression to tension area's wiil then'be greatly increased and the results improved. If the-perimeter binding oftho cones is tightened, when the system is otherwise-set, the results will'be'still further improved showing that compressive strains are more effective and preferable to tension strains. lVhere a double cone of pleated construction is used as just described, and where the system is under a strain of conside able magnitude which is carried near to the point of actuation, I secure great tidelity of reproduction and brilliance of detail together with great volume, in addition to which there is a very considerable increase in efficiency over what has yet been accomplished. By etiiciency I mean a greater response for a given amount of energy. Pleated double cones provide a greater range of action in that there is more give between the apices and as the pitch which can be faithfully reproduced is a function of the area of the sound generator, I lind that the pleated double cone can go to much lower limits of pitch and that this pitch can be varied by varying the stress in the system by means of the knurled nut, 11. Therefore I may tune the sound generator to various pitches such as concert or international, and this may be done while the generator is functioning. Another advantage of the double pleated cone that it is not critical as to pitch but may be easily tuned and retained at that pitch and furthermore, no open bezel is necessary as has heretofore been thought indispensable to procure clarity of tone.

Instead of using the pleated double cone I may use a pleated single cone of similar construction to that of my copending application for sound reproducers, Serial No. 152.091, the perimeter of which would preferably seat upon some strong rigid retaining ring to serve an abutment for the vanes when under compression. The system would then be balanced under stress as heretofore described. In using such a cone I would secure excellent results but without the range or ctliciency of the double cone, added to which is the fact that a single cone is critical as to the adjustment for pitch.

\Vbile 1 have described my system of sound generation as including pleated cones either double or single,] may eipially well use plain cones and while the quality of reproduction and the volun'ie would be superior to what is now available, such plain cones would fall short of the quality and volume of reproduction secured from the pleated cones but under certain circumstances I may choose to use cones having plain surfaces.

In my sound reproducers I use a material possessing resiliency and rigidity such as the impregnated Japanese vellum mentioned.

IVhile I prefer to use a relatively light material such as this vellum, I am not limited thereto but may use other and heavier materials with rectangular or trapezoidal pleats (particularly for large cones) as set forth in my copending application for sound reproducers, Serial No. 152,091; it being understood that in the invention of this application. the use of stresses of considerable magnitude overcomes the inertia ellects well as providing the benefits and advantages already described. l urthermore, when pleats of trapezoidal shape are used, I secure a better distribution of mass throughout the area of the sound generator and also in relation to the stress. The small ends of the trapezoids being at the center, there a smaller mass at that point and a better and less clumsy connection to the rest of the system is possible.

In Fig. :2 is shown my system of sound generation adapted to use with an electromagnetic actuating unit. The pleated cones are shown at and 26 with the upper edges or ridges of the pleats shown at 27 and :28. and the lower edges at 29 and so; the perimeters being joined as indicated by the line 31. In like manner to Fig. I the outer apex of cone 25 has a cone seat, 52, through which passes the threaded piece, 33, carrying the knurled nut, 34. The apex of the inner cone, 26, also seats upon a cone, 35, fixed to the unit. 36. Fixed to the threaded member. 33. and passing through openings in the cone seat. 35. and the frame of the unit, 36, is a wire or tension element, 37. This wire, 37. is atlixed to the lever. 38, seated upon the fulcrum. 39. as shown. The lever, 38. has an opening through which passes the cap screw, threaded into the frame of the unit, 3b. and upon which is mounted a compi ssion spring, 4i, acting between the head of the cap screw and the lever. At the opposite end of the lever from this cap screw is a screw. 412. which serves to retain the rod or wire, 43, in an opening provided in the lever. The wire, 43, is fastened to the oscillating member, 44, pivoted at 45. The unit, 36. has its usual frame, 4-6. carrying pole pieces 47 and 48 and the field coils. 49.

This adaptation of my sound geueratii'ig system utilizes the same principles as described under Fig. 1. The knurled uut'. ll-l. provides an adjustable means for creating compression in the vanes of the pleated cones. 25 and 2n, and this compression may be brought up to the point of the st renglh of the cone n'iateriai 2: id the tension upon the Wire. 37, is balanced at the lever. :38. by the spring, 41, which is itself adjustable by means of the cap screw. 40. Consequently there is again a balanced system obtained with the cones in the required degree of com 'iression, the wire, 37, in tension and all being balanced in the lever, 38. The actuation of the system takes place from the oscillation of the nu mber. 44, as caused by the field coil, 49, in conjunction with the pole pieces. This actuation is imparted to the lever, 38, by the wire. 43. It will be noticed that the only neutral portion of the entire apparatus is that which includes th member, 44, and the wire. 43. and this is main tained in a neutral condition by setting the screw, 42. 'lherefore, not only is the whole lib) system under stress but that stress is brought close to the point of actuation and, as heretofore described, there is an energy condition wherein all lost motion and inherent conipressibility 0r elasticity is taken up. and energv imparted to the system from the unit will be all used in creating vibrations in the cones by varying the stress therein.

1 have heretofore described the material composing, and the formation oi, these cones which included the desirability oi light weight to avoid inertia eli'ects. To this end the (one seat. 32. of Fig. 2, as well as seat 9 of Fig. l, are made of any suitable material. and the tension means attached to them are preferably wire or rods of a size sutticient to withstand the tension placed upon them.

In Fig. 3 is a further adaptation of my system to an electromagnetic unit wherein the actuating energy is applied directly instead of through a lever as in Figures 1 and It is customary in phonographic and in electromagnetic units to have the arms of the lever in the reducing ratio of about 2/3 to l, and this has become more or less standard. Attempts have been made to apply the actuating energy directly to the sound generator but heretofore such disadvantages have appeared as to make this conimercially unsuccesstul. dowever, I have found that a structure such as indicated in Fig. 3, successfully accomplishes this r suit with equal it not greater benefits than the lever construction shown in the previous figures. To this end cones 50 and 51. are constructed and joined as heretofore described. The upper cone has a similar cone seat, 52, a knurled nut, 58, carried by threaded member, 54. The lower cone rests upon cone 55 ot' the unit. This unit is of the type known as jump coil wherein the frame and pole pieces are at 56, the field coil." at 57, and the jump coil at this jump coil being spanned by the yoke, 59. The unit has a hollow central portion in which is seated the cap, (it). carrying the threaded member, (ii. and a compression spring seated in the hollow portion. l lxtending between tne threaded members, 5% and 61, and fastened thereto is the wire or tension member, (32. which not only passes through the unit as shown but is fixedly attached at 63 to the yoke, of the jump coil. As already stated the cones may be placed under much compression as desired and the tension set up in the wire, ('32. balanced by the spring acting against the threaded member, 6i, so that the jump coil. 58. will be carried directly on the wire, 62. Here it will be seen that stresses set up in the s vs tem are not only balanced but are led directly to the point of actuation which is at 63. Consequently. when in operation whatever moven'ient occurs in the jump coil, 58. is imparted directly to the cones, 50 and 51. Here there is no lost motion whatever to be taken up and the cones having been placed in an initial energy condition, the reproduction in this system will be equal to it not superior to the two systems previously described.

From the foregoing it is clear that my invention covers a principle not yet known or used by others nor taught by the prior art and it is essentially one of creating high initial stress in the sound generator, and carrying that near or to the point of actuation and there balancing it; the sound production being a result of variations in the stress caused by the actuator.

I am aware that many changes and modifications may be made in my invention without departing from the spirit thereof and I include all such changes and variations within the scope of my claims.

I claim 1. A system of sound generation which comprises a sound generator under compressive. stress, means to create that stress and other means to balance the stress creating means.

2. A system of sound generation which comprises a ound generator under compressive stress, means to create that stress, an actuating unit and means to balance said stress creating means clcse to the point of actuation in said unit.

3. A system of sound generation comprising a double cone under compressive stress, means to adjust that stress and means to actuate said cones by varying the stress therein.

4. A system of sound generation which comprises a sound generator and an actuating unit, adjustable tension means arranged to create compressive stresses in said generator and means within the unit to balance said tension means.

5. A system of sound generation which includes a sound generator and an actuating unit, adjustable tension means acting between said generator and said unit, and adapted to set up compressive strains in said generator and means to actuate said generator by actuating said tension means.

6. A system oi sound generation wherein sounds are generated by varying the stress in a sound generator initially under compressive stress.

7. A system of sound generation wherein sounds are generated by varying the stresses in a sound generator initially under compressive and torsional stresses.

8. A system of sound generation which includes a hollow sound generator, means to create a compressive stress in the. Walls of said generator and means to generate sound by varying said stress.

9. A system of sound generation which includes a pleated, hollow sound generator, the elements of which are maintained under compression.

10. A system of sound generation including a double cone sound generator from the lit) apex of one of which a tension is created, an actuating unit and means associated with said unit to balance said tension.

11. A system of sound generation which includes a sound generator in which compressive stresses of considerable magnitude are created by tension means and other means di rectly to actuate said tension means.

12. A system of sound generation which includes a sound generator in which compressive stresses of considerable magnitude are created by tension means, means to balance said tension and means to actuate said tension means.

13. A systen'i of sound generation, which includes a pleated sound generator having torsional stresses in the pleats, tension means coacting with and adapted to set up compressive stresses of considerable magnitude in said generator, means to balance the tension of said tension means and means to actuate the tension nieans.

14. A system of sound generation which includes a double cone sound generator and an actuating unit, adjustable means arranged to cause the api'ces of said cones to approach each other, means associated with said unit to balance the adjustable means and other means within the unit to actuate the balancing means.

15. A system of sound generation which includes a cone sound generator having a rigidly supported perimeter, an actuating unit, adjustable tension means acting between the apex of said cone and said unit, means associated with said unit to balance said tension means and other means associated with said unit to actuate said tension means.

16. The method of generating sound which comprises placing a body under compressive stress of considerable magnitude and then varying that stress.

17. The method of generating sound which comprises placing a body under compression by applying a tension to a selected point of said body and then varying said tension.

18. The method of generating sound which comprises placing a body under torsional and compressive stresses and then varying said stresses.

In Witness whereof, I have hereunto subscribed my name this 30th day of November,

CHARLES P. MADSEN. 

